Recent advances in endocrine therapy of breast cancer

New Entrants into Clinical Trials for Targeted Therapy of Breast Cancer: An Insight

Breast cancer is too complex with various different molecular alterations involved in its pathogenesis and progression. Over the decade, we have seen a surge in the development of drugs for bimolecular targets and for the signal transduction pathways involved in the treatment line of breast cancer. These drugs, either alone or in combination with conventional treatments like chemotherapy, hormone therapy and radiotherapy, will help oncologists to get a better insight and do the needful treatment. These novel therapies bring various challenges along with them, which include the dosage selection, patient selection, schedule of treatment and weighing of clinical benefits over side effects. In this review, we highlight the recently studied target molecules that have received indications in breast carcinoma, both in the localized and in an advanced state and about their inhibitors which are in clinical development which can give the immense potential to clinical care in the near future.

Exostosin 1 regulates cancer cell stemness in doxorubicin-resistant breast cancer cells

Cancer stem cells (CSCs) are associated with cancer recurrence following radio/chemotherapy owing to their high resistance to therapeutic intervention. In this study, we investigated the role of exostoxin 1 (EXT1), an endoplasmic reticulum (ER)-residing type II transmembrane glycoprotein, in cancer cell stemness. DNA microarray analysis revealed that doxorubicin-resistant MCF7/ADR cells have high levels of EXT1 expression compared to its parental cell line, MCF7. These cells showed significantly higher populations of CSCs and larger populations of aldehyde dehydrogenase (ALDH⁺) and CD44⁺/CD24^-cells, as compared to MCF7 cells. siRNA-mediated knockdown of EXT1 in MCF7/ADR cells significantly reduced cancer stem cell markers, populations of ALDH⁺and CD44⁺/CD24^- cells, mRNA and protein expression for CD44, and mammosphere number. Furthermore, epithelial mesenchymal transition (EMT) markers and migratory behavior were also repressed with reduced EXT1. In an in vitro soft agar colony formation assay, EXT1 knockdown by short hairpin RNA (shRNA) reduced the colony formation ability of these cells. Based on these results, we suggest that EXT1 could be a promising novel target to overcome cancer cell stemness in anthracycline-based therapeutic resistance.

Cryptotanshinone inhibits proliferation and induces apoptosis via mitochondria-derived reactive oxygen species involving FOXO1 in estrogen receptor-negative breast cancer Bcap37 cells

Cryptotanshinone inhibits proliferation and induces apoptosis of the estrogen receptor-negative breast cancer Bcap37 cells via FOXO1 inhibition and ROS-mediated PI3K/AKT/mTOR signaling pathways.

Trends in 1-year survival of people admitted to hospital in Ontario, 1994-2009

BACKGROUND

Changes in the long-term survival of people admitted to hospital is unknown. This study examined trends in 1-year survival of patients admitted to hospital adjusted for improved survival in the general population.

METHODS

One-year survival after admission to hospital was determined for all adults admitted to hospital in Ontario in 1994, 1999, 2004, or 2009 by linking to vital statistics datasets. Annual survival in the general population was determined from life tables for Ontario.

RESULTS

Between 1994 and 2009, hospital use decreased (from 8.8% to 6.3% of the general adult population per year), whereas crude 1-year mortality among people with hospital admissions increased (from 9.2% to 11.6%). During this time, patients in hospital became significantly older (median age increased from 51 to 58 yr) and sicker (the proportion with a Charlson comorbidity index score of 0 decreased from 68.2% to 60.0%), and were more acutely ill on admission (elective admissions decreased from 47.4% to 42.0%; proportion brought to hospital by ambulance increased from 16.1% to 24.8%). Compared with 1994, the adjusted odds ratio (OR) for death at 1 year in 2009 was 0.78 (95% confidence interval [CI] 0.77-0.79). However, 1-year risk of death in the general population decreased by 24% during the same time. After adjusting for improved survival in the general population, risk of death at 1 year for people admitted to hospital remained significantly lower in 2009 than in 1994 (adjusted relative excess risk 0.81, 95% CI 0.80-0.82).

INTERPRETATION

After accounting for both the increased burden of patient sickness and improved survival in the general population, 1-year survival for people admitted to hospital increased significantly from 1994 to 2009. The reasons for this improvement cannot be determined from these data.

A Case of Complete Response to Letrozol Treatment in a Postmenopausal Woman With Breast Cancer Who has Progressed After Multiple Lines of Chemotherapy

Approximately 60% of all breast cancers are endocrine dependent. Postmenopausal patients who have positive hormone receptor status are eligible for aromatase inhibitor treatment. Letrozole is a potent, selective, non-steroidal, third-generation aromatase inhibitor which reduces oestrogen biosynthesis approximately 99% at the dose of 2.5 mg/day. We report a 54-years-old female patient diagnosed with grade 2 invasive ductal carcinoma of the breast. She received adjuvant chemotherapy, followed by 5 years of tamoxifen. After 8 years, recurrence appeared in lung, supraclavicular lymph nodes and brain. She had many cycles of cytotoxic chemotherapeutic agents, trastuzumab and lapatinib previously. After the progression (lung and brain), palliative therapy was thought due to very poor performance status of the patient. (ECOG: 3) Letrozole was added in the treatment and we obtained near-complete remission from her lung and brain metastasis with 2.5 mg/day dose of letrozole. This study might support successfully use of aromatase inhibitors in patients who has been previously treated with multiple lines of chemotherapy and had still progressive disease.

Effects of cyclin D1 gene amplification and protein expression on time to recurrence in postmenopausal breast cancer patients treated with anastrozole or tamoxifen: a TransATAC study

INTRODUCTION

Gene amplification of CCND1 is observed in a subgroup of breast cancers with poor prognosis, whereas overexpression of the protein cyclin D1 has been linked to both worse and better clinical outcome. CCND1 amplification and protein overexpression have also been associated with resistance to treatment with tamoxifen or even to a potentially detrimental effect of tamoxifen.

METHODS

To clarify these challenging and partly contrasting treatment predictive and prognostic links for cyclin D1 we analysed a large cohort of postmenopausal breast cancer patients randomised to receive either adjuvant anastrozole or tamoxifen, as part of the Arimidex, Tamoxifen, Alone or in Combination (ATAC) trial. The CCND1 amplification status and protein expression of cyclin D1 were assessed by chromogenic in situ hybridisation and immunohistochemistry, respectively, in 1,155 postmenopausal, oestrogen-receptor-positive breast cancer patients included in the TransATAC substudy.

RESULTS

Amplification of CCND1 was observed in 8.7% of the tumours and was associated with increased risk of disease recurrence (hazard ratio = 1.61; 95% confidence interval, 1.08 to 2.41) after adjustment for other clinicopathological parameters. In contrast, nuclear expression of cyclin D1 protein was associated with decreased recurrence rate (hazard ratio = 0.6; 95% confidence interval, 0.39 to 0.92). The intensity of nuclear or cytoplasmic expression was not of prognostic value. There was no significant interaction between cyclin D1 status and treatment efficacy, ruling out any major detrimental effect of tamoxifen in CCND1-amplified postmenopausal breast cancer.

CONCLUSIONS

In summary, CCND1 amplification and low nuclear expression of cyclin D1 predicted poor clinical outcome in postmenopausal breast cancer patients treated with either anastrozole or tamoxifen.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN18233230.

Aromatase inhibitors for treatment of advanced breast cancer in postmenopausal women

BACKGROUND

Endocrine therapy removes the influence of oestrogen on breast cancer cells and so hormonal treatments such as tamoxifen, megestrol acetate and medroxyprogesterone acetate have been in use for many years for advanced breast cancer. Aromatase inhibitors (AIs) inhibit oestrogen synthesis in the peripheral tissues and have a similar tumour-regressing effect to other endocrine treatments. Aminoglutethimide was the first AI in clinical use and now the third generation AIs, anastrozole, exemestane and letrozole, are in current use. Randomised trial evidence on response rates and side effects of these drugs is still limited.

OBJECTIVES

To compare AIs to other endocrine therapy in the treatment of advanced breast cancer in postmenopausal women.

SEARCH STRATEGY

For this update, the Cochrane Breast Cancer Group Specialised Register and the Cochrane Central Register of Controlled Trials (CENTRAL) and relevant conference proceedings were searched (to 30 June 2008).

SELECTION CRITERIA

Randomised controlled trials in postmenopausal women comparing the effects of any AI versus other endocrine therapy, no endocrine therapy, or a different AI in the treatment of advanced (metastatic) breast cancer. Non-English language publications, comparisons of the same AI at different doses, AIs used as neoadjuvant treatment, or outcomes not related to tumour response were excluded.

DATA COLLECTION AND ANALYSIS

Data from published trials were extracted independently by two review authors and cross-checked by a third. Hazard ratios (HR) were derived for analysis of time-to-event outcomes (overall and progression-free survival). Odds ratios (OR) were derived for objective response, clinical benefit, and toxicity.

MAIN RESULTS

Thirty-seven trials were identified, 31 of which were included in the main analysis of any AI versus any other treatment (11,403 women). No trials were excluded due to inadequate allocation concealment. The pooled estimate showed a significant survival benefit for treatment with an AI over other endocrine therapies (HR 0.90, 95% CI 0.84 to 0.97). A subgroup analysis of the three commonly prescribed AIs (anastrozole, exemestane, letrozole) also showed a similar survival benefit (HR 0.88, 95% CI 0.80 to 0.96). There were very limited data to compare one AI with a different AI, but these suggested an advantage for letrozole over anastrozole.AIs have a different toxicity profile to other endocrine therapies. For those currently prescribed, and for all AIs combined, they had similar levels of hot flushes and arthralgia; increased risks of rash, nausea, diarrhoea and vomiting; but a 71% decreased risk of vaginal bleeding and 47% decrease in thromboembolic events compared with other endocrine therapies.

AUTHORS' CONCLUSIONS

In women with advanced (metastatic) breast cancer, aromatase inhibitors including those in current clinical use show a survival benefit when compared to other endocrine therapy.

Effect of anastrozole and tamoxifen on lipid metabolism in Japanese postmenopausal women with early breast cancer

Endocrine therapies that profoundly decrease estrogen levels potentially have a detrimental effect on the cardiovascular system. This study evaluated the effect on lipid metabolism of one such agent, the new generation aromatase inhibitor anastrozole, compared with tamoxifen, when used as adjuvant treatment in postmenopausal Japanese women with early breast cancer. All patients had completed primary surgery and were randomized to anastrozole 1 mg once daily (n=22) or tamoxifen 20 mg once daily (n=22). Anastrozole significantly reduced levels of triglycerides and remnant-like particle cholesterol, whereas tamoxifen significantly increased these. Activity of lipoprotein lipase and levels of high-density lipoprotein cholesterol significantly increased after anastrozole treatment. In contrast, activity of hepatic triglyceride lipase, also a key enzyme of triglyceride metabolism, significantly decreased following treatment with tamoxifen. We thus conclude that in our study anastrozole had a beneficial effect on lipid profiles of postmenopausal women with early breast cancer after 12 weeks of treatment.

Adjuvant Endocrine Therapy in Premenopausal Patients

Endocrine adjuvant therapy is the best-described molecular targeted treatment and should therefore be used for all patients with endocrine-responsive breast cancer. Ta-moxifen for 5 years is standard of care and has proven efficacy in premenopausal patients. The combination of tamoxifen with ovarian function suppression and/or chemotherapy has been extensively tested, and some controversial approaches are used in clinical practice. Cessation or suppression of ovarian function appears to be beneficial for premenopausal patients. Particularly for premenopausal women with highly endocrine-responsive disease and/or low risk for relapse, the additional benefit of cytotoxic chemotherapy may be minor or nonexistent. While the use aromatase inhibitors is investigated in clinical trials, their application outside an academic trial setting cannot be recommended based on first available results. In contrast, the use of adjuvant bispho-sphonates may offer another strategy of further improving clinical outcomes in this important patient subgroup.

Do endocrine treatments for breast cancer have a negative impact on lipid profiles and cardiovascular risk in postmenopausal women?

Although cardiovascular disease occurs infrequently in premenopausal women, the incidence increases dramatically after menopause. Endocrine agents used to treat postmenopausal women with breast cancer further reduce estrogen levels and have the potential to adversely affect lipid metabolism, although the relevance of this to cardiovascular risk remains uncertain. Until recently, the standard endocrine treatment for breast cancer was tamoxifen, which appears to have a generally favorable effect on lipid parameters, although this does not translate into cardioprotective effects. The third-generation aromatase inhibitors (AIs), including anastrozole, have recently emerged as alternatives for the treatment of postmenopausal women with hormone-sensitive breast cancer. Anastrozole, currently the only AI with established long-term safety data in the adjuvant setting, results in significantly fewer thromboembolic and cerebrovascular events compared with tamoxifen, and a similar incidence of ischemic cardiovascular events. However, the effects of other AIs on lipid values are variable, and any relationship with cardiovascular events in long-term studies is currently unknown.

Aromatase inhibitors for treatment of advanced breast cancer in postmenopausal women

BACKGROUND

Hormonal treatments for advanced or metastatic breast cancer, such as tamoxifen and the progestins megestrol acetate and medroxyprogesterone acetate, have been in use for many years. Aromatase inhibitors (AIs) are a class of compounds that systemically inhibit oestrogen synthesis in the peripheral tissues. Aminoglutethimide was the first AI in clinical use (first generation) and had a similar tumour-regressing effect to other endocrine treatments, which showed the potential of this alternative type of therapy. Other AIs have since been developed and the third generation AIs anastrozole, exemestane and letrozole are in current use. Randomised evidence on response rates and side effects of these drugs is still limited.

OBJECTIVES

To compare aromatase inhibitors to other endocrine therapy in the treatment of advanced breast cancer in postmenopausal women.

SEARCH STRATEGY

The Cochrane Breast Cancer Group Specialised Register was searched on 3 December 2004 using the codes for "advanced" and "endocrine therapy". Details of the search strategy applied to create the Register and the procedure used to code references are described in the Cochrane Breast Cancer Group module on The Cochrane Library. The search was updated to 30 September 2005 and additional publications were included. Experts were consulted to determine that no relevant studies had been excluded.

SELECTION CRITERIA

Randomised trials comparing the effects of any aromatase inhibitor versus other endocrine therapy, no endocrine therapy or a different aromatase inhibitor in the treatment of advanced (metastatic) breast cancer.

DATA COLLECTION AND ANALYSIS

Data from published trials were extracted by two independent review authors. A third independent author then carried out a further cross check for accuracy and consistency. Hazard ratios (HR) were derived for analysis of time-to-event outcomes (overall and progression-free). Odds ratios (OR) were derived for objective response and clinical benefit (both analysed as dichotomous variables). Toxicity data were extracted where present and treatments were compared using odds ratios. All but one of the studies included data on one or more of the following outcomes: overall survival, progression-free survival, clinical benefit and objective response.

MAIN RESULTS

Thirty studies were identified, twenty five of which were included in the main analysis of any AI versus any other treatment (9416 women). The pooled estimate showed a significant survival benefit for treatment with an AI over other endocrine therapies (HR 0.89, 95%CI 0.82 to 0.96). A subgroup analysis of the three commonly prescribed AIs (anastrozole, exemestane, letrozole) also showed a similar survival benefit (HR 0.88, 95%CI 0.80 to 0.96). The results for progression-free survival, clinical benefit and objective response were not statistically significant and there was statistically significant heterogeneity across types of AI. There were very limited data to compare one AI with a different AI, but these suggested an advantage for letrozole over anastrozole. All the trials of AIs used exclusively as first-line therapy were against tamoxifen. There was an advantage to treatment with AIs in terms of progression-free survival (HR 0.78, 95% CI 0.70 to 0.86) and clinical benefit (OR 0.70, 95% CI 0.51 to 0.97) but not overall survival or objective response. There was considerable heterogeneity across studies when considering clinical benefit (P = 0.001). Use of an AI as second-line therapy showed a significant benefit in terms of overall survival (HR 0.80, 95% CI 0.66 to 0.96) but not for progression-free survival (HR 1.08, 95% CI 0.89 to 1.31), clinical benefit (OR 1.00, 95% CI 0.87 to 1.14) or objective response (OR 0.96, 95% CI 0.81 to 1.14). This is difficult to interpret due to the extreme heterogeneity across AIs for progression-free survival but not the other endpoints.AIs have a different toxicity profile to other endocrine therapies. For all AIs combined, they had similar levels of hot flushes (especially when compared to tamoxifen) and arthralgia, increased risks of nausea, diarrhoea and vomiting, but a decreased risk of vaginal bleeding and thromboembolic events compared with other endocrine therapies. A similar pattern of risks and benefits was still seen when analyses were limited to the currently most-prescribed third generation AIs.

AUTHORS' CONCLUSIONS

In women with advanced (metastatic) breast cancer, aromatase inhibitors including those in current clinical use show a survival benefit when compared to other endocrine therapy.

Biotransformation of letrozole in rat liver microsomes: effects of gender and tamoxifen

The in vitro metabolic kinetics of letrozole were investigated by incubating letrozole (10-500 microM) in female or male rat liver microsomes to assess the effect of gender and to predict the in vivo biotransformation characteristics of letrozole in rats. The effects of tamoxifen (TAM) on the metabolic kinetics of letrozole were also examined by incubating letrozole in female rat liver microsomes in the presence or absence of TAM. The effects of chronic pretreatment of female rats with TAM (0.5, 1.0, 5.0 mg/kg/day, i.p. for 7 consecutive days) on liver microsomal protein content and metabolic activity were also examined. The formation rate of the carbinol metabolite of letrozole, CGP44 645, was significantly higher (p<0.05) in male rat liver microsomes in comparison to female. The V(max)/K(m) ratio for letrozole metabolism in female rat liver microsomes did not change significantly (p>0.05) in the presence of TAM. After chronic pretreatment of female rats with TAM (up to a dose of 1.0mg/kg/day), the hepatic microsomal protein content was significantly increased but the formation rate of CGP44 645, when normalized for protein content, did not change significantly. These results suggest that there is a marked gender difference in letrozole metabolism in rats. It also appears that acute treatment of female rat liver microsomes with TAM produces negligible inhibitory effect on the CYP mediated metabolic clearance of letrozole. However, chronic pretreatment of female rats with TAM appear to induce CYPs, but does not significantly impact the metabolic activities of the enzymes associated with the formation of the carbinol metabolite of letrozole.

Antiestrogens, aromatase inhibitors, and apoptosis in breast cancer

Antiestrogens have been the therapeutic agents of choice for breast cancer patients whose tumors express estrogen receptors, regardless of menopausal status. Unfortunately, many patients will eventually develop resistance to these drugs. Antiestrogens primarily act by preventing endogenous estrogen from activating estrogen receptors and promoting cell growth, which can ultimately lead to tumor cell death. Understanding the mechanisms by which antiestrogens cause cell death or apoptosis is critical to our efforts to develop ways to circumvent resistance. This article focuses on antiestrogen-induced apoptosis both in vitro and in vivo. We review the clinical utility of both antiestrogens and aromatase inhibitors and their apoptogenic mechanisms in cell culture models. Among the key signaling components discussed are the roles of Bcl-2 family members, several cytokines, and their receptors, p53, nuclear factor kappa B (NFkappaB), IRF-1, phosphatidylinositol 3-kinase (PI3K)/Akt, and specific caspases. Finally, we discuss the evidence supporting a role for apoptotic defects in acquired and de novo antiestrogen resistance.

Clinical significance of the expression of estrogen receptors alpha and beta for endocrine therapy of breast cancer

The assessment of the estrogen receptor (ER) alpha and the progesterone receptor (PgR) in breast cancer tissues is important for discriminating between hormone-dependent and hormone-independent tumors. ERbeta, a more recently discovered ER, may influence estrogen action through the ERalpha pathway. To evaluate the clinical significance of these receptors in the response to endocrine therapy, we investigated their expression in primary breast cancer tissues. ERalpha and PgR were evaluated using immunohistochemistry (IHC) and enzyme immunoassay (EIA) and ERbeta expression was determined using IHC and reverse transcription-polymerase chain reaction. When the cut-off level of EIA was set at 13 fmol/mg protein for ERalpha and that for IHC was set as an IHC score between 2 and 3, a significant correlation between ERalpha EIA and IHC was seen (concordance rate 88.4%). This indicates that this cut-off level of ERalpha IHC can be adopted to quantify breast cancer prognoses. Furthermore, the tumors with positive expression of ERalpha IHC or PgR IHC using this criterion were significantly related to the response to endocrine therapy. Additionally, tumors with positive expression of ERbeta wild-type tended to have a better response to endocrine therapy than negative ones, and tamoxifen responders tended to exhibit a lower ratio of ERbetacx (one of the ERbeta variants) to ERbeta wild-type than nonresponders. The results concerning ERbeta are not yet fully understood; further investigations and evaluations should analyze the role of ERbeta wild-type and variant type in breast cancer treatment.

Anastrozole alone or in combination with tamoxifen versus tamoxifen alone for adjuvant treatment of postmenopausal women with early breast cancer: first results of the ATAC randomised trial

BACKGROUND

In the adjuvant setting, tamoxifen is the established treatment for postmenopausal women with hormone-sensitive breast cancer. However, it is associated with several side-effects including endometrial cancer and thromboembolic disorders. We aimed to compare the safety and efficacy outcomes of tamoxifen with those of anastrozole alone and the combination of anastrozole plus tamoxifen for 5 years.

METHODS

Participants were postmenopausal patients with invasive operable breast cancer who had completed primary therapy and were eligible to receive adjuvant hormonal therapy. The primary endpoints were disease-free survival and occurrence of adverse events. Analysis for efficacy was by intention to treat.

FINDINGS

9366 patients were recruited, of whom 3125 were randomly assigned anastrozole, 3116 tamoxifen, and 3125 combination. Median follow-up was 33.3 months. 7839 (84%) patients were known to be hormone-receptor-positive. Disease-free survival at 3 years was 89.4% on anastrozole and 87.4% on tamoxifen (hazard ratio 0.83 [95% CI 0.71-0.96], p=0.013). Results with the combination were not significantly different from those with tamoxifen alone (87.2%, 1.02 [0.89-1.18], p=0.8). The improvement in disease-free survival with anastrozole was seen in the subgroup of hormone-receptor-positive patients, but not the receptor-negative patients. Incidence of contralateral breast cancer was significantly lower with anastrozole than with tamoxifen (odds ratio 0.42 [0.22-0.79], p=0.007). Anastrozole was significantly better tolerated than tamoxifen with respect to endometrial cancer (p=0.02), vaginal bleeding and discharge (p<0.0001 for both), cerebrovascular events (p=0.0006), venous thromboembolic events (p=0.0006), and hot flushes (p<0.0001). Tamoxifen was significantly better tolerated than anastrozole with respect to musculoskeletal disorders and fractures (p<0.0001 for both).

INTERPRETATION

Anastrozole is an effective and well tolerated endocrine option for the treatment of postmenopausal patients with hormone-sensitive early breast cancer. Longer follow-up is required before a final benefit:risk assessment can be made.

Tamoxifen resistance in breast cancer: elucidating mechanisms

Tamoxifen has been used for the systemic treatment of patients with breast cancer for nearly three decades. Treatment success is primarily dependent on the presence of the estrogen receptor (ER) in the breast carcinoma. While about half of patients with advanced ER-positive disease immediately fail to respond to tamoxifen, in the responding patients the disease ultimately progresses to a resistant phenotype. The possible causes for intrinsic and acquired resistance have been attributed to the pharmacology of tamoxifen, alterations in the structure and function of the ER, the interactions with the tumour environment and genetic alterations in the tumour cells. So far no prominent mechanism leading to resistance has been identified. The recent results of a functional screen for breast cancer antiestrogen resis- tance (BCAR) genes responsible for development of tamoxifen resistance in human breast cancer cells are reviewed. Individual BCAR genes can transform estrogen-dependent breast cancer cells into estrogen-independent and tamoxifen-resistant cells in vitro. Furthermore, high levels of BCAR1/pl30Cas protein in ER-positive primary breast tumours are associated with intrinsic resistance to tamoxifen treatment. These results indicate a prominent role for alternative growth control pathways independent of ER signalling in intrinsic tamoxifen resistance of ER-positive breast carcinomas. Deciphering the differentiation characteristics of normal and malignant breast epithelial cells with respect to proliferation control and regulation of cell death (apoptosis) is essential for understanding therapy response and development of resistance of breast carcinoma.

Comparison of the systemic and intratumoral effects of tamoxifen and the aromatase inhibitor vorozole in postmenopausal patients with primary breast cancer

PURPOSE

To determine biologic differences, if any, between presurgical endocrine treatment with an aromatase inhibitor (vorozole) and tamoxifen in patients with postmenopausal primary breast cancer.

PATIENTS AND METHODS

Randomization was to 12 weeks of 2.5 mg of vorozole per day or 20 mg of tamoxifen per day, both orally. Clinical response was assessed monthly together with serum sex hormone binding globulin (SHBG), luteinizing hormone (LH), follicle-stimulating hormone (FSH), estrogens (E1, E2, and E1S), lipids, insulin-like growth factor-1 (IGF-1), and bone metabolites (CrossLaps CTx). Tissue samples for Ki67, apoptotic index (AI), estrogen receptor, and progesterone receptor were collected at 0, 2, and 12 weeks.

RESULTS

Ki67 fell by 58% and 43% (means) at 2 weeks in the vorozole and tamoxifen patients, respectively (P =.13). In the vorozole group, the correlations of proportional changes in Ki67 at 2 weeks with tumor volume changes and clinical response at 12 weeks were not significant (P =.09) and marginally significant (P =.04), respectively. Serum lipids did not differ between groups. Serum levels of EI, E2, and E1S were suppressed markedly by vorozole, whereas levels of SHBG increased and LH and FSH fell significantly with tamoxifen. IGF-1 levels fell significantly with tamoxifen (P =.001) compared with the nonsignificant rise with vorozole. Twelve-week CTx values fell by 19% with tamoxifen (P =.006) and rose by 11% with vorozole (P =.15).

CONCLUSION

The correlation with vorozole of Ki67 with volume and clinical response supports this as an intermediate marker. The nonsignificant effects on bone and lipid metabolism by the aromatase inhibitor may be important to consider for adjuvant and potential prevention strategies.

Has tamoxifen had its day?

Tamoxifen is probably the most important drug in the history of the management of breast cancer and its development is a tribute to cross talk between laboratory scientists and clinical investigators. Its use as adjuvant therapy has led to a decrease of 20-30% in age-adjusted cause-specific mortality in the developed world and it is approved in the USA for the chemoprevention of breast cancer in high-risk women. The recent ATAC and IBIS trials have challenged the supremacy of tamoxifen. The present paper is a personal view of the implications for the future use of this drug in competition with the oral aromatase inhibitors. In the opinion of the author tamoxifen will probably remain the mainstay for adjuvant therapy of postmenopausal women with hormone-responsive disease, but maturation of the ATAC data may allow a choice in selected cases. Anastrozole looks like a competitor for the future but we may have to wait another 10 years to find out.

Formestane, a steroidal aromatase inhibitor after failure of non-steroidal aromatase inhibitors (anastrozole and letrozole): is a clinical benefit still achievable?

BACKGROUND

There are few clinical data on the sequential use of aromatase inhibitors (AI). This paper focuses on the relevance of clinical benefit CB (CR + PR + SD > or = 6 months) in postmenopausal metastatic breast cancer (MBC) patients treated with the steroidal aromatase inhibitor (SAI) formestane (FOR). who had already received non-steroidal aromatase inhibitor (nSAI): letrozole (LTZ) or anastrozole (ANZ).

PATIENTS AND METHODS

Twenty postmenopausal women with MBC were analysed in this retrospective two-centre study with the sequence nSAI-FOR. When receiving ANZ, 1 of 11 achieved a complete response and 9 of 11 a stable disease > or = 6 months, and receiving LTZ 1 of 9 achieved a partial response and 4 of 9 a stable disease > or = 6 months. The analysis of the entire population treated with FOR showed an overall CB of 55% (11 of 20) with a median duration of 15 months and median time to progression (TTP) of 6 months.

CONCLUSIONS

Formestane 250 mg once bi-weekly seems to be an attractive alternative third-line hormonal therapy for the treatment of patients with MBC, previously treated with nSAI.

Pharmacokinetics of anastrozole and tamoxifen alone, and in combination, during adjuvant endocrine therapy for early breast cancer in postmenopausal women: a sub-protocol of the 'Arimidex and tamoxifen alone or in combination' (ATAC) trial

The ATAC trial evaluates in a randomized, double-blind design, Arimidextrade mark (anastrozole) alone or in combination with tamoxifen, relative to tamoxifen alone as 5-year adjuvant treatment in postmenopausal women with early breast cancer. Patients included in the pharmacokinetic (PK) sub-protocol had been in ATAC for > or =3 months, taking their medication in the morning and were 100% compliant for the preceding 14 days. Blood samples were collected 24 +/- 4 h after last dose. Trough (C(min)) plasma concentrations of anastrozole, tamoxifen and desmethyltamoxifen (DMT) were measured by validated methods. The PK results were based on a total of 347 patients (131 anastrozole (1 mg o.d.), 111 tamoxifen (20 mg o.d.), 105 anastrozole and tamoxifen (1 and 20 mg o.d. respectively)). The geometric mean steady-state trough plasma concentrations of tamoxifen and DMT were statistically equivalent in patients receiving tamoxifen alone or in combination with anastrozole: geometric mean tamoxifen = 94.8 ng ml(-1)and 95.3 ng ml(-1)in tamoxifen alone and combination groups, respectively; geometric mean DMT = 265.1 and 277.6 ng ml(-1)in the tamoxifen and anastrozole and tamoxifen groups, respectively. The geometric mean anastrozole levels were 27% lower (90% Cl 20-33%;P< 0.001) in the presence of tamoxifen than with anastrozole alone. Baseline plasma oestradiol levels were not obtained in the PK sub-protocol, however, such information was available from a similar ATAC sub-protocol, which evaluated bone mineral density. Mean oestradiol levels were 21.3, 19.3, and 21.6 pmol l(-1)prior to treatment and 3.7, 20.9 and 3.6 pmol l(-1)after 3 months in the anastrozole, tamoxifen, and combination groups, respectively (n = 167). On-treatment values were below the detection limit (3 pmol l(-1)) in 43.6 and 38.5% of the anastrozole alone and anastrozole in combination with tamoxifen groups, respectively. As a result of (a) the lack of effect of anastrozole on tamoxifen and DMT levels and (b) the observed fall in blood anastrozole levels having no significant effect on oestradiol suppression by anastrozole, we conclude that the observed reduction in anastrozole levels by tamoxifen is unlikely to be of clinical significance when anastrozole and tamoxifen are administered together.

Breast carcinomas with immunocytochemical detection of aromatase in fine-needle aspirates: report of three cases

Three postmenopausal women with breast carcinoma underwent the fine-needle aspiration (FNA) preoperatively, and these specimens were stained by the antiaromatase antibody. We evaluated the identification of the aromatase immunoreactivity in breast carcinoma specimens obtained from both FNA and surgery. FNA specimens showed positive intracellular immunoreactivity of aromatase in these cases. The presence for aromatase in FNA specimens was identified with that in the surgical specimens. To our knowledge, the present cases are the first to report the aromatase staining of FNA specimens. The immunoreactivity of aromatase in FNA specimen may be useful to estimate the effectiveness of new aromatase inhibitors in patients with breast carcinoma. HUM PATHOL 32:348-351.

Recent advances in the clinical application of aromatase inhibitors

Aromatase inhibitors have evolved over a period of 20 years to well tolerated agents that can effectively obliterate aromatase activity in postmenopausal women. Breast cancer is the predominant clinical application and here the newer agents have established themselves as the preferred second-line agent after tamoxifen in the treatment of advanced disease. Recent data indicate that they be more efficacious than tamoxifen and, therefore, may replace it as the first-line agent of choice in the near future. On-going clinical trials in the adjuvant setting and prospective prevention studies will elucidate whether these drugs have a yet greater role in breast cancer.

Vorozole results in greater oestrogen suppression than formestane in postmenopausal women and when added to goserelin in premenopausal women with advanced breast cancer

The high potency and selectivity of new aromatase inhibitors has translated to greater efficacy and improved tolerability in comparison with established second-line hormonal agents for advanced breast cancer in phase III clinical trials. Two pharmacological studies are reported which assess the use of one of these inhibitors, vorozole, in combination or comparison with well-established methods of oestrogen deprivation in pre and postmenopausal patients. When combined with the gonadotrophin-releasing hormone agonist (GnRHa) goserelin in 10 premenopausal patients, vorozole markedly enhanced the suppression of serum levels of oestrone, oestradiol and, oestrone sulphate beyond that achieved by goserelin alone (by a mean 74%, 83%, and 89%, respectively). The combination was well-tolerated and had no significant effects on androgen levels. Vorozole was compared with formestane in 13 postmenopausal women and serum oestrone, oestradiol, and oestrone sulphate levels were suppressed by 47%, 30%, and 70%, respectively, more by vorozole than by the steroidal aromatase inhibitor. Again the tolerability was excellent. The plasma oestrogen levels in the postmenopausal patients on vorozole were lower than in the premenopausal patients on goserelin plus vorozole, indicating that ovarian oestrogen synthesis may be relatively resistant to aromatase inhibition, even during GnRHa treatment. Thus, in both pre and postmenopausal patients substantially greater suppression of oestrogen can be achieved by vorozole compared with alternative approaches. Existing clinical-pharmacological correlates suggest that these increases in pharmacological effectiveness may result in enhanced clinical effectiveness.

Anastrozole shows evidence of activity in postmenopausal patients who have responded or stabilised on formestane therapy

Formestane (Lentaron) and anastrozole (Arimidex) are in clinical use as second-line treatments for advanced breast cancer. Current practice is often to use an aromatase inhibitor only once before switching to third-line agents such as progestins. There are few clinical data on the sequential use of aromatase inhibitors. We therefore decided to study the clinical effects of anastrozole in postmenopausal patients with advanced breast cancer who had already received formestane. 21 patients were recruited. When receiving formestane 2/21 (10%) achieved a partial response (UICC criteria) and 10/21 (48%) stable disease. Of these 12 patients, 9 achieved further stable disease on anastrozole (78%; 7/9 oestrogen receptor positive). 4 of 9 patients who progressed on formestane also stabilised on anastrozole, of whom 3 had oestrogen receptor positive breast carcinomas. The explanation of this second stabilisation may relate to a further fall in oestradiol levels. We feel these results are of interest and warrant further clinical investigation.

The effect of anastrozole on the pharmacokinetics of tamoxifen in post-menopausal women with early breast cancer

Thirty-four post-menopausal women with early breast cancer who had received 20 mg tamoxifen once daily as adjuvant therapy for at least 10 weeks participated in a randomized, double-blind, parallel-group, multicentre trial. The primary aim of the trial was to determine the effect of anastrozole upon tamoxifen pharmacokinetics, with secondary aims of assessing the tolerability of the two drugs in combination and whether or not tamoxifen had any effect upon the oestradiol suppression seen with anastrozole. Patients were randomized to receive either 1 mg anastrozole (16 patients) or matching placebo (18 patients) once daily on a double-blind basis for 28 days. No significant difference (P = 0.919) was observed in serum tamoxifen concentrations between the anastrozole and placebo groups during the trial. The serum concentration of oestradiol was significantly suppressed (P < 0.0001) in patients co-administered anastrozole compared with placebo in the presence of tamoxifen, confirming that anastrozole remained an effective suppressant of oestradiol in the presence of tamoxifen. The combination of tamoxifen and anastrozole was well tolerated, with very little difference in side-effects reported between anastrozole and placebo. In conclusion, the results of this study confirm that anastrozole does not affect the pharmacokinetics of tamoxifen when the two drugs are given in combination to post-menopausal women with early breast cancer. In addition, the oestradiol suppressant effects of anastrozole appear unaffected by tamoxifen.